An extrusion process has been broadly used for producing various tubes for aluminum heat exchangers, which are used for heat exchangers such as evaporators, condensers, and radiators since the melting point of aluminum, which is a raw material, is low.
In such an extrusion process, as shown, for example, in FIG. 8, an aluminum raw material (billet) 103 is inserted into a hole of a container 102 to which a die 101 is attached at an end thereof, the aluminum raw material 103 in the container 102 is pressed toward an opening 105 provided in the die 101 by a stem (pressurizing plate) 104, the aluminum raw material 103 is extruded through a gap having a constant cross-section shape and provided in the opening 105, and whereby the material is extruded so as to be an extruded part having a constant cross-section shape. According to this extrusion process, it is possible to obtain an extruded part having a very complicated shape through a single deformation process by applying compressive force to the aluminum raw material 103 inserted into the container 102.
FIG. 9 shows an example of a flat multi-hole tube 106 for an aluminum heat exchanger, which is formed through an extrusion process of aluminum. Conventionally, an insert type die disclosed in Patent Document 1 has been known as an extrusion die device which is suitable for producing the extruded flat multi-hole tube 106.
An example of a conventional insert type die device disclosed in Patent Document 1 is shown in FIGS. 10 and 11. A die 100 of this example is provided to produce the extruded flat multi-hole tube 106 of aluminum shown in FIG. 9 through an extrusion process, and includes a pair of a female die 111 and a male die 112 having a thick circular-disc shape and being engageable and detachable, which are insertable into and detachable from through holes H provided in a circular-disc shaped die holder D shown in FIG. 11.
In FIG. 10, the female die 111 includes an annular centering recess 113 provided at the outer periphery of an end surface facing the male die 112, and a recess 115 is provided in a enter end surface 114 of the centering recess 113. Furthermore, a slit-shaped hole 116 extending from an end to the other end along the center axis of the female die 111 is provided at the center portion of the recess 115. Moreover, two threaded holes 119 and two pin holes 120 are provided in a symmetrical manner at locations surrounding the recess 115.
In FIG. 10, the male die 112 includes a centering projection 122 provided at the outer periphery of an end surface facing the female die 111. A comb-shaped projected portion 123 consisting of a plurality of projected pieces is provided at the center portion of the male die 112. The projected portion 123 is provided to be inserted into the hole 116 of the female die 111 so as to form a gap (molding hole), which defines the shape of a product, between the projected portion 123 and the hole 116. Furthermore, the male die 112 is provided with through holes 124 extending along the both sides of the projected portion 123 and opening into both surfaces of the male die 112. Moreover, the male die 112 is provided with two threaded holes 125 and two pins 126 around the through holes 124.
Moreover, the die 100 is configured by integrating the male die 112 and the female die 111 having a configuration as described above into a circular column shape while engaging the centering recess 113 and the entering projection 122 and engaging the pins 126 and the pin holes 120. An extrusion process can be performed by attaching four dies 100 to the disc-shaped die holder D shown in FIG. 11, and by attaching the whole device to the container 102 shown in FIG. 8. Furthermore, the die 100 having this configuration provides an advantage such as an economical point when compared with an integrated type die because, when one of the dies 100 in the die holder D fails, an extrusion process can be resumed by only replacing the particular die 100 or by only replacing either the particular female die 111 or the particular male die 112.
Furthermore, the applicant of the present application has filed a patent application relating to a die having a configuration in which a portion of a projected portion for forming a molding hole in an extrusion process can be replaced as a core member separately from the other parts of a male die (refer to Patent Document 2).
According to the technology disclosed in Patent Document 2, the male die is constituted by providing a core member having a projected portion and a core case to which the core member is attached, the core member is made of cemented carbide having a high wear resistance, and the core case is made of ordinary die steel, whereby, it is possible to increase the life of the die, and to enhance replaceability when encountering partial wear or breakage.